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Further advancements in engine development lead to increased fuel efficiency and reduced CO₂ emission. Such low emission engine concepts require most advanced exhaust gas aftertreatment systems for lowest possible tailpipe emissions. On the other hand, the exhaust gas purification by catalytic measures experiences more and more challenges due to constantly reduced exhaust gas temperatures by more efficient engines. These challenges can be overcome by traditional catalyst heating strategies, which are known to increase fuel consumption and emissions. Alternatively, electrically heated catalysts ("EHC") can be utilized to provide a very efficient method to increase gas temperatures directly in the exhaust catalyst. This way the energy input can be tailored according to the component need and the energy loss in the system can be minimized.

Beginning with the interim Tier 4 legislation in the US, off-highway engines with 56 - 560 kW are required to reduce Particulate Matter (PM) emissions to less than 0.02 g/kWh. While this significant reduction in PM emissions represents a great new challenge for off-highway engines, it can be achieved with a combination of engine measures and PM aftertreatment technologies. An engine with high engine out PM emissions would require a wall flow filter which has to be frequently actively regenerated at temperatures above 600 degree C and requires measures to address ash collection. On the other hand, an engine with low to moderate engine out PM emissions could be fitted with a passively regenerated partial filter such as the PM-Metalit, with no need for frequent high temperature soot regeneration or ash removal maintenance [1, 2]. A PM-Metalit system is constructed solely from metal and thus is extremely robust against severe mechanical loads that are present in off-highway applications.

Modern powertrain systems, both diesel and gasoline, have achieved an extremely high level of complexity in order to comply with customer demands on performance, fuel efficiency, comfort, as well as regulatory requirements. This leads to relatively high costs of the complete engine and exhaust gas after-treatment system of a vehicle. Therefore, every component needs to be optimized. Metallic substrate catalyst components have been developed and manufactured with optimized fluid dynamic and turbulent flow characteristics leading to smaller components, offering equal or better performance compared to conventional straight channel substrates. The smaller, advanced metal substrate components are easier to package, can be installed closer to the engine, weigh less, and can reduce the necessary precious metal content. This helps in conserving natural resources, and enables original equipment manufacturer to meet their technical targets at lower costs.

The current study focuses on the operating behavior of a NOx-adsorber catalyst upstream of a Diesel particulate filter as two separate exhaust gas aftertreatment components. New European drive cycle (NEDC), US FTP 75, and US06 tests with a NOx-adsorber have been performed with and without a DPF in two passenger cars with initial test weights (ITW) between 1550 and 1750 kg. Transient particle size distributions have also been measured during FTP 75 and US06 tests. Also on road driving with a NOx-adsorber and DPF has been carried out. During these tests, the focus has been on the NOx-adsorber catalyst and on the interaction between the NOx-adsorber and the DPF. The purge events to regenerate the NOx-adsorber (rich exhaust gas composition,λ < 1) have been controlled automatically via new engine control unit functionalities. These algorithms have been developed using the rapid prototype tool ETAS ASCET.